LANUS, Argentina, April 14 (Reuters) - Daniel Scioli, the front-running candidate for the ruling party ticket in Argentina's presidential election, has a new buzz word: "gradualismo", or "gradual change".

It is hardly a slogan to set the campaign trail ablaze ahead of the October 25 election. Instead it illustrates the tightrope act he needs to pull off as he tries to win the support of outgoing leftist President Cristina Fernandez's loyalists while tapping a rich vein of undecided voters demanding c...